https://doi.org/10.15255/KUI.2002.016
Published: Kem. Ind. 52 (6) (2003) 243–250
Paper reference number: KUI-16/2002
Paper type: Professional paper
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Selection of Membrane Elements and Calculation of Technical Characteristics of Membrane Unit for Production of Potable from Surface Water

K. Košutić and B. Kunst+

Abstract

The objective of this work was to show an approach to selection and calculation of technical quantities of the membrane unit for production of potable from surface water. A technically optimal membrane proces to decrease the concentrations of natural organic matter and hardnes of water was looked for. Two types of nanofiltration modules were selected: the NF1 module with a high rejection factor for both the organic matter and the water hardnes, and the NF2 module with a high rejection factor for the organic matter and a lower rejection of divalent ions. The proces quantities and technical characteristics of the two-stage membrane units using the first and the second selected modules, were calculcated and compared. The unit using the NF1 type modules showed the satisfactory high organics rejection and too high hardnes rejection (according to the Croatian standards for drinking water), along with the good permeate yield of 87 %. In case of the unit with NF2 modules the rejection of calcium was too low. On the basis of the obtained results the combined unit having the NF1 modules in the first stage and the NF2 modules in the second stage was calculated. The results were improved, and in order to increase the permeate yield a part of the first stage retentate was recycled. The permeate yield was increased to 91 % of the feed water. The final result was the unit that showed the following advantages: the satisfactory high removal of organic pollutants the satisfactory (according to the Croatian standards for drinking water) removal of hardnes, the high yield of the permeate (drinking water) approximately the same number of modules as in the other, conventional solutions, which means that the investment costs would not be higher.

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Keywords

reverse osmosis, nanofiltration, membrane modules, technical quantities calculation, surface water treatment, potable water production